Ternary Imides for Hydrogen Storage

Abstract

(see Fig. 2 in the Supporting Information): a large heat of adsorption means greater stabilization of the adsorbed methane. The heat of adsorption of methane by europium-nitrate-dispersed SWNH at all density regions of adsorbed methane is greater than that of an as-grown SWNH by 40±90 meV.In conclusion, we have obtained the following results:d 1) A small amount of dispersed lanthanides strongly enhances the methane adsorption.d 2) Adsorbed methane molecules are stabilized by dispersed lanthanide nitrates on the SWNH.This enhancement effect of methane storage is only observed with carbon nanohorns (see Supporting Information). Currently we have only applied this method to as-grown SWNHs. However, enhancement of gas adsorption by charge transfer is promising as a means for achieving practical methane storage. ExperimentalObservation by STEM: The sample of europium-nitrate-dispersed SWNHs was put on a holey carbon grid disk and observed by a scanning transmission electron microscope (HD2000-UHV, Hitachi, 120 kV).Determination of Pore Volume of SWNHs: After pretreatment at 423 K and 1 mPa, the pore volume of the SWNHs was determined volumetrically by a nitrogen-adsorption isotherm at 77 K with a volumetric apparatus (Autosorb 1, Quantachrome) [2]. The nitrogen-adsorption isotherms were analyzed with the a s -method described by Sing [6]. The specific surface areas and micropore volumes of SWNH samples are shown in Table 1.Methane Adsorption: We measured the amount of methane adsorbed by a gravimetric method at 303 K by using an electric microbalance (Cahn 1100) [7] with a resolution of 0.1 lg. In order to remove adsorbed gases and water, a pretreatment was performed at a pressure of less than 1 mPa and temperature of 423 K for 2 h prior to the adsorption measurement.The adsorbed-methane density could not be obtained directly from the experiments. We therefore had to calculate it from the experimental adsorbed amount (surface excess mass). [8] We assumed that the adsorbed-methane density is given by [9] q ad = (C/V 0 ) + q bulk (1) where q ad (g L ±1 ) is the adsorbed-methane density, C (mg g ±1 ) is the experimental adsorbed-methane amount, V 0 (mL g ±1 ) is the pore volume of the SWNH, and q bulk is the density of methane in the bulk gas phase.Sample Preparation: The SWNH was synthesized by CO 2 laser ablation of graphite under Ar gas at 101 kPa [1]. Lanthanide nitrates were dispersed on the as-grown SWNH as lanthanide nitrate solution. The SWNH was mixed with an ethanolic lanthanide nitrate solution and this mixture was sonicated for five minutes. Finally, the mixture of lanthanide nitrate solution and SWNH was dried at room temperature for a week.Received Ternary Imides for Hydrogen Storage** By Zhitao Xiong, Guotao Wu, Jianjiang Hu, and Ping Chen*The demand for highly efficient solid-state hydrogen storage materials for the coming hydrogen economy has encouraged tremendous efforts in the development of novel systems such as complex chemical hydrides and carbonaceous materials.[1±4] Metal nitrides and imides, newc...

Solid–Solid Heterogeneous Catalysis: The Role of Potassium in Promoting the Dehydrogenation of the Mg(NH2)2/2 LiH Composite

“…This system possesses a relatively high reversible hydrogen content ( % 5.6 wt %) [12][13][14] and suitable thermodynamic properties that allow its dehydrogenation at 1 bar equilibrium pressure at temperatures below 90 8C. [15] However, dehydrogenation at an appropriate rate usually requires temperatures above 180 8C even if the composite has undergone intensive ball milling, which shows the existence of a severe kinetic barrier in the dehydrogenation.…”

Recent Progress and New Perspectives on Metal Amide and Imide Systems for Solid-State Hydrogen Storage

“…40 kJ/mol. The reaction between LiNH 2 and MgH 2 (or Mg(NH 2 ) 2 and LiH) for hydrogen storage was reported for the first time in 2004 by five different groups [48][49][50][51][52]. They investigated several factors in the reaction including different ratios between amide and hydride and ab/desorption conditions.…”

“…They investigated several factors in the reaction including different ratios between amide and hydride and ab/desorption conditions. Xiong et al [52] heated lithium amide and magnesium hydride in a 2:1 molar ratio up to 350 • C, and, similar to the Li-N-H system, only hydrogen, without any ammonia, is desorbed. It is found that the hydrogen desorption temperatures are lower than in the LiNH 2 + LiH system.…”

Hydrogen Storage Properties of the Mg(NH<SUB>3</SUB>)<SUB>6</SUB>Cl<SUB>2</SUB>-LiH Combined System

“…11) A variety of metal amide-hydride combinations have been designed and developed for their hydrogen storage performances. [11][12][13][14][15] However, most of them still suffer from the high operating temperature for practical applications.…”

“…1) In contrast to the compressed hydrogen and the liquefaction hydrogen, hydrogen storage in the solid state is the most promising alternative. [2][3][4][5] In the past decades, the complex hydrides consisting of light elements, e.g., alanates, [6][7][8][9][10] amides, [11][12][13][14][15] borohydrides [16][17][18][19][20] and ammonia borane (AB), [21][22][23] have been attracting extensive attention as the potential hydrogen storage materials due to their high gravimetric and volumetric hydrogen storage densities. In particular, significant efforts have been made in recent years with metal amide-hydride combined systems since Chen et al reported that lithium nitride, Li 3 N could absorb/desorb reversibly 11.4 mass% of hydrogen in 2002.…”